First, there are inner and outer constant velocity joint boots, two on each side. It is common, especially the outer ones closest to the tire, for them to tear or crack especially when driving on gravel roads and in winter conditions where ice can also slice away at the rubber. Second, it is not oil but grease that comes out of the boots. I want to make sure that the technician is not scaring you into a repair simply because you ran over some oil on the road or splashed something up into your wheel well, and he is trying to dupe you into a repair. PLEASE find yourself a trusted local mechanic in your area. http://www.repairpal.com
will guide you to one in your area and will give you a basic quote for such a repair. Then you will know if you are being cheated with the quote you mentioned.
The common noise alerting a driver that a CV boot is cracked is when one makes a full hard turn in either direction. If the grease has emptied out of the boot, you will hear a screeching or scratching noise while the car is moving and turning. If there indeed is a tear of one (or more) of the boots, any technician can easily show you the tear while the car is up on a lift unless the tear is on the very top side of the boot. Good luck.